The air supplied to the carburetor or other fuel-air mixing means of an internal combustion engine is customarily filtered to remove solid particles which might clog the carburetor or other fuel-air mixing device or might damage the engine. In an automobile, the air filter is customarily a sizable device which is housed in the engine compartment. However, an air filter of this kind is too bulky and cumbersome to be used on a small internal combustion engine such as those used for filament type trimmers, lawn mowers and chain saws. The air filter of such engines is customarily a small static-type filter comprising porous, fibrous or foraminous material through which the air passes and which is intended to filter out solid particles. However, such a filter becomes quickly clogged when the engine operates in a dirty environment as in the case of a filament type trimmer, garden tiller or lawn mower which operates close to the ground and in the case of a chain saw which produces saw dust and may kick up dirt either from a tree or log being cut or by inadvertant contact with the ground. In order to keep the engine operating properly, the air filter must be frequently changed or cleaned.